If you add the top and bottom of the part, the resulting material "removal" leaves a part that is 1/2 inch on top, 1/2 inch second step and 1 1/4 inch third step. Just look at the part you have left after Backplotting! You can clearly see it if you compare the two views, BobCad and Predator.
Watch the video again and count the steps for the last level and you will see that it makes five 1/4 inch passes for a total of 1.25 inches.
I'm not arguing procedure or preferences of machining here, just pointing out a glitch in the program when entering top and bottom.
I remember another part that I made that got changed when I added the top and bottom of the part, but at that time I thought I did something wrong and just eliminated the top and bottom and did not think about it again, until now. There is a bug or something that is in that part of the program.
I am not trying to bash BobCad, I'm just pointing out a bug. I respect you and all that you do here and I have defended you in other posts, but this is obviously a problem. Perhaps BobCad can fix this and help everyone out.
I used part of the program and added to it and took away and finished my parts on Friday, so this is now just academic.